ENVIRONMENTAL SEALING

Abstract: A warning whistle that is activated by over-inflation of an inflatable duct seal. The warning whistle is preferably used in conjunction with an inflation tool (20) with an outlet tube (9) which may be connected to an inflatable duct seal. The tool (20) carries a pressure release valve (21) at an outlet of which the whistle (14) of the invention is attached.

Description: ENVIRONMENTAL SEALING The present invention relates to a warning instrument for use in environmental sealing of substrates such as cables or pipes, particularly within a duct, or a splice case. Such sealing may be done to prevent water, gas or other contaminant from passing along a duct into a manhole etc, or to protect a cable splice from the environment. The invention will be described primarily in terms of a duct seal, (which term includes " c 5edthroughs") but the invention is also applicable to other instanc of sealing, including splice cases, pipe protection and grommets etc. WO92/19034 (Raychem) discloses a flexible hollow sealing member (preferably having substantially non-stretchable walls) that can be inflated to seal a gap between first and second articles and that has: a hole directly through a wall or between walls thereof through which hole a probe can be inserted (and from which it can preferably be removed by mere pulling) to introduce pressurizing medium into the member, and means by which the hole is automatically sealed on withdrawal of the probe. It may be desirable that some warning system be provided to indicate excessive pressure in order that damage to the sealing member or to the thing sealed be avoided. Such a warning system is preferably audible. We have, however, discovered that presently available whistles and other similar instruments are unsuitable for our purpose. We have further discovered that the air flow rate required by such known whistles is far too high, and as a result have designed a new instrument. Thus, the present invention pro lies an instrument that produces an audible tone in response to passage of a gas at a flow rate below 600 ml per second, preferably below 100 ml per - 9 - second, and more preferably at flow rates throughout the range 40-100 ml per second. The instrument of the present invention preferably forms part of a pressure relief valve which may be connected somewhere in the line used to inflate the sealing member. If the pressure exceeds a certain level, generally between 2.5 and 5 bar, particularly between 3 and 4 bar, the pressure relief valve will open preventing excessive pressure building up in the sealing member. It is desirable that the operator know that an excessive pressure has occurred so he can shut-off or reduce the supply of gas, and the instrument of the invention can provide audible warning to this end. The instrument is preferably connected, by welding, bonding, or screwing etc or is integral with the relief valve so that at least part, and preferably all, of the released gas passes to it. An internal flap may be provided across the hole in or between the walls of the member. The flap may seal in response to pressure within the member. The flap preferably comprises a flexible polymeric sheet fixed to a wall of the member such that the probe can pass through the hole and displace the flap, the probe preferably passing between the flap and the wall substantially in the plane of the wall (say at less than 45° to that plane). A sealing material, for example a gel or a mastic, may be provided between the flap and the wall, for example as a coating on the flap. The flap may be bonded or welded to the wall along two lines separated by a small gap (say 5-20 mm), such that the probe can be inserted through the hole in the wall and between the wall and the flap generally along the axis of the channel formed between the two bond or weld lines. The hole may be between overlapping walls of a lap join. (The lap join may arise in formation of the member by forming a tube from a sheet of material.) The hole, which extends the width of the lap join, may decrease in cross-sectional size toward the outside of the sealing member. The hole may therefore have a funnel, or flattened-funnel, shape. A sealing material (preferably a mastic or a gel) may be provided within this funnel-or-other- shaped hole, such that the sealing material is driven by internal pressure to block the hole. The size of the hole and the physical properties and amount of the sealing material may be chosen such that the material does not creep out of the hole to an unacceptable extent. A flap as mentioned above may be used in conjunction with this type of hole. The sealing material may comprise for example a mastic or a gel. Mastics may be preferred due to their good adhesion to the wall of the sealing member. A seal can therefore remain even on loss of some or all of the internal pressure that forces the flap against the wall. Mastics however have high, generally 100%, compression set and where that is likely to be a problem the mastic may be replaced or supplemented by a gel. For example if the probe is likely to leave a channel in the mastic on withdrawal, a gel could be provided as a supplementary layer between the mastic and the wall, preferably of smaller surface area than (and therefore totally surrounded by) the mastic. A gel may be formed by oil-extension of a polymeric material. The polymeric material may be cross-linked. We prefer that the gel have a hardness at room temperature as determined using a Stevens-Volland Texture Analyser of greater than 45g, particularly greater than 50g especially greater than 60g. It preferably has a stress-relaxation less than 12%, particularly less than 10% and especially less than 8%. Ultimate elongation, also at room temperature, is preferably greater than 60%, especially greater than 1000%, particularly greater than 1400%, as determined according to ASTM D638. Tensile modulus at 100% strain is preferably at least 1.8, more preferably at least 2.2 MPa. In general compression set will be less than 35%, especially less than 25%. Preferred gels are made by extending with an oil block copolymers having hard blocks and rubbery blocks. Examples include triblock copolymers of the styrene-ethylene-butylene-styrene type (such as those known by the Shell Trade Mark Kraton, eg G1650, 1651 and 1652). The amount of block copolymer may be, say from 5 - 35% of the total weight of the gel, preferred amounts being 6 - 15%, especially 8 - 12%. The amount of copolymer, and its molecular weight may be varied to give the desired physical properties such as hardness. The designs described above will find particular use for environmental protection of supply lines such as pipes and cables particularly telecommunications cables. In particular, they may be used for the formation of duct seals or splice cases. In the case of duct seals, the first article as referred to above will comprise a cable carried by a duct, and the second article will comprise the duct. The duct seal will seal the annular space between the cable and the duct, and serve to prevent contaminants, in particular water, passing along the duct, for example into a manhole or building or other region to be kept dry or clean. Pressure may build up in the duct, and it is therefore desirable that means be provided for restricting movement of the duct seal along the duct in response to a pressure difference across it. Inflation may be carried out by attaching a tube to a source of pressurizing fluid and (if it is not supplied in place) inserting the tube through the hole in the wall or between walls of the sealing member. The pressurizing fluid is preferably compressible, air or nitrogen or other inert gas being preferred. The sealing member may be stretchable but we prefer that it is not, and that pressurization of the fluid alone allows for compensation for movement of the first and second surfaces. If the sealing member is stretchable it is likely to be subject to creep or set. We prefer therefore that it have minimal stretch and that a gas be used for inflation. The tube, when inserted, will provide a path past the internal sealing flap or sealing material allowing the fluid to inflate the sealing member. The sealing member, being flexible, will deform into sealing engagement with the first and second articles, for example by filling an annulus between a cable and a duct within - which it lies. A seal can be made inspite of lack of concentricity between duct and cable, and inspite of oval or other awkward cross-sectional shapes of the cable and/or duct. When the desired internal pressure is reached, the tube may be simply withdrawn, allowing the internal pressure automatically to close the hole. Astonishingly, high internal pressures can be achieved and a seal that will last for many years can be made in this way. The tube is preferably held in position prior to and/or during inflation merely by friction and/or by weak adhesion, allowing it easily to be pulled free. There is preferably no mechanical interlocking. The tube is preferably therefore substantially cylindrical at least at the end that enters the sealing member. The tube may comprise metal or a plastics material and may have a low coefficient of friction with the flap, the wall and/or any sealing material between them in order to facilitate removal. It is desirable that inflation be not too rapid since the sealing member itself, and any sealing material it carries must deform properly into sealing engagement with cable and duct. A hand pump (such as a bicycle pump), an electric pump, a pressurized gas cylinder or other suitable pressurizing means may be used. More powerful pumps may desirably be used with a pressure reducer. The envelope is wrapped or otherwise positioned around a cable within a duct (for example by sliding it into the duct) and then inflated with any suitable medium, such as air or other gas. The envelope deforms to fill the space between the duct and the cable. Deformation is preferably without significant stretching, say less than 6%, particularly less than 4% in length, and less than 12%, particularly less than 9% in width. Any stretching preferably occurs within a few days of installation, with no subsequent creep. The wall of the sealing member will in general be preferably flexible, and thus able to conform to substrates of various sizes and/or of irregular or awkward shape. It may comprise at least three layers, for example one serving to retain the fluid, one to provide mechanical strength for example tensional strength against internal pressure, tear-strength or puncture resistance and one layer serving to form a seal to the substrate by accommodating small scale irregularities in the surface of the substrate. To this end the wall may comprise a first layer of metal (or metallized plastics material or metal-coated plastics material) optionally with which the fluid is in contact, and a second strengthening layer such as high density polyethylene, together with a third layer, in direct or indirect face-to-face relation with the first layer, and positioned between the first layer and the substrate. The third layer referred to above may comprise a deformable material such as a rubber or other elastomer or a foam. Other materials may be used as this third layer, for example sealing materials such as sealants, for example as referred to above. Additional layers may be provided for mechanical strength such as oriented, for example biaxially-oriented or two layers of uniaxially oriented, high density polyethylene such as that known by the trade mark Valeron. A possible structure is as follows; the dimension being merely preferred. Copolymer 15 - 30 microns. Valeron (trade mark) 40 - 160 microns Mylar (trade mark) 10 - 30 microns Aluminium (as one or more layers) 5 - 60 microns Mylar (trade mark) 10 - 30 microns Linear low density Polyethylene 0 - 80 microns Copolymer 15 - 30 microns An alternative structure comprises Rayofix T (trade mark) 75 - 125 microns Polyester "O" (such as Mylar) 75 - 125 microns Aluminium 8 - 16 microns Polyester "O" (such as Mylar) 75 - 125 microns Rayofix T 75 - 125 microns "Rayofix" is a terpolymer comprising ethylene butylacrylate, acrylic acid and ethylene groups. The sealing member preferably comprises a substantially flat (which term includes flattenable, since the article may be set in a curved or similar shape) flexible envelope that can be wrapped around an elongate substrate such as a cable to form an annulus which can be deformed by internal pressure to increase its radial thickness. In this way, an annular gap between a duct and a cable it carries may be sealed. The invention is further illustrated by the accompanying drawings, in which: Figure 1 shows a duct seal in use; Figures 2a to 2d show the formation of a splice case; Figure 3 shows a sealing member; Figures 4a to 4c show inflation of a sealing member; Figures 5a to 5e show an instrument for producing a tone; Figure 6 shows an inflation tool; Figure 7 shows a pressure-relief valve; Figure 8 shows a test apparatus; and Figures 9a to 9j show various designs of instrumen In Figure 1 a sealing member 1 is shown as a duct seal, sealing an annular gap between a cable 2 (the first article as referred to above) and a duct 3 (the second article). The sealing member 1 has flexible, and preferably substantially non- stretchable, walls 4 between which a pressurizing fluid 5 such as air is introduced. An outer surface of the walls 4 may be provided with a sealing material 6, such as a mastic, to fill irregularities in the surface of the duct. Figures 2a to 2d show the sealing member used to seal an outlet of a cable splice case 7 housing a branched cable splice or two pipes. Figure 2a shows two cables 2 leaving a housing which may comprise at least part of a cable splice case or pipe enclosure. A cross-section near the end of the housing is shown in figures 2b and 2c. In figure 2b one sealing member 1 has been wrapped around the two cables and is shown before inflation. In figure 2c two sealing members 1 are used one around each cable. The effect of inflating the sealing member is shown in figure 2d. The sealing member can be seen to seal the space between the housing and the cables 2 thus preventing contaminants entering the splice case. (Overlapping layers of the sealing member are shown slightly separated for clarity.) The housing of figure 2d is of the wraparound type, a closure being shown at 8. A sealing member 1 is shown in a partially wrapped-around configuration in figure 3. Figure 3 also shows a tube 9 penetrating a hole 10 in a wall of the sealing member through which a fluid may be introduced. A covering 11 , such as cling film, is shown partially covering the sealing material 6 in order that a less tacky surface be presented to the duct for easy installation. A self-sealing valve is shown in figures 4a to 4c. The valve comprises a sealing material 12 such as a gel on an internal surface of a wall of the sealing member. The sealing material may be held in place by a flap 13. A tube for inflating the sealing member is forced through a wall thereof. The hole 10 through which the tube 9 passes may be preformed in the wall or is maybe formed by the tube 9 when required. Figure 4a is a perspective view showing the tube 9 in position, figure 4b is a cross-sectional view of the tube in position, and figure 4c shows the effect of withdrawal of the tube 9 after inflation is complete. The sealing material can be seen to protrude slightly through the hole 10 due to internal pressure acting on the sealing material 12 and flap 13. In this way the hole 10 is self sealing. The instrument of the invention is used to warn the installer against over inflation of the sealing member and therefore the instrument may be connected in the tube 9, in some other part of the inflation system, or in the sealing member directly. The instrument will be positioned such that the inflating fluid passes to and preferably through the instrument or otherwise activates it, if an excessive pressure develops. This can perhaps most easily be arranged by connecting the instrument to the outlet of a pressure-relief valve the inlet of which is in communication with the inside of the sealing member. A preferred design of instrument is shown in figures 5a to 5c. This instrument 14 has a fipple 15 as its sound generator, and it may be regarded as a simple whistle. It comprises a tubular body having a cut in its surface acting as the fipple, and having an inlet airway at one end formed by shaped block 17 and having its opposite end closed by block 18. The fipple preferably has a cross-sectional area from 20-250 mm 2 , more preferably from 30- 150 mm 2 , especially from 50-100 mm 2 . Figure 5b shows a perspective view of the whistle, figure 5c shows a cross-sectional view, and figures 5d and 5e show the blocks 17 and 18. The instrument may act as a Helmholtz resoL--.or, preferably having a resonating volume from 500-6000 mm 3 , more preferably from 700-3000 mm 3 , especially from 800-1500 mm 2 . An airway through which the gas must pass and which leads to the sound generator preferably has a cross-sectional area of 2- 10 mm 2 - The instrument may have a screw thread 19 or other means for securing it to a pressure -relief valve etc. We have surprisingly discovered that commercially available whistles are not, in general, suitable for our purposes. We have discovered that the pressures and air speeds at which they operate are far too high. We prefer a whistle that will produce a clear tone at very low air speeds and that will therefore indicate opening of a pressure release valve immediately it occurs. Also, we prefer that the whistle can pass air at a high volume rate in order that the whistle does not itself produce a back pressure. The tone that the whistle produces is preferably between 100 and 10000 Hz, particularly from 500 to 4000 Hz and most preferably between 500 and 2000 Hz. We therefore prefer that the whistle produce an audible tone in response to passage of a gas at a flow rate below 600 ml per second, preferably below 100 ml per second. We prefer that an audible tone is produced at speeds throughout the range from 20 to 100 ml per second, and preferably down to 10 ml per second and more preferably down to virtually zero flow rate. For whistles of preferred size (cylindrical and about 16 mm in diameter) a flow rate of 600 ml litres per second corresponds to a linear speed of 3 metres per second, and a flow rate of 100 ml per second corresponds to a flow rate of 0.5 metres per second. Even at these low flow rates the intensity of the tone produced is preferably at least 60 dB, more preferably at least 90 dB. The table below, giving a range of air speeds (in m/s) for whistles of various dimensions, is provided to allow the reader to design a suitable whistle that will produce a audible tone for a variety of air speeds. The table gives values in mm for the dimensions A to K of figure 5a. In each of the fourteen examples illustrated in the table the whistle comprised a tube of diameter 16 mm and the air speed was measured for an inlet pressure of 5.5 Bar. The instrument of the invention is preferably used in conjunction with an inflation tool 20 as illustrated in figure 6. This inflation tool has an outlet tube 9 which may be connected to an inflatable sealing member. The tool 20 carries a pressure- release valve 21 at an outlet of which the instrument 14 of the invention is attached. A suitable pressure-release valve is illustrated in figure 7. This valve is available from IMI Norgren Limited of Warwickshire, England under the designation Series 61A2 or 61B2. The valve comprises a body 22 containing a valve assembly 23 which, under normal pressures, prevents passage of gas through the body. The valve assembly is held in place by a spring 26 acting on spring rest 24 which abuts the valve assembly. A lock nut 25 is used to secure an adjusting cap 27 at the correct position to produce the desired pressure on the spring. The instrument of the invention may be screwed, welded, bonded, ' or otherwise fixed to the top of the valve as drawn. The inflation tool 20 illustrated in figure 6 may have various other features such as diameter reduction, by means of which pressure may be reduced, means 29 for connection to a source of pressurized gas, a gauge 30, and an on-off control 31. Various different types of whistles, some commercially available, and some new, were compared using the test apparatus shown in figure 8. (It should be noted that the combination of any of these whistles with an inflatable sealing member is novel.) This apparatus consisted of an air chamber 32 to one end of which each whistle 14 was connected. Air was introduced into the other end of the chamber by means of a pipe 34 and the purpose of the test was to compare the sound emitted by the whistle for various air speeds. A probe 35 was inserted into the chamber to measure the air speed which was displayed on a meter 36. The intensity of the sound produced was measured by means of a dB meter 37. The apparatus also included a gauge 30 and a control lever 33. A successful result is one in which a clear tone was produced at low air speeds and substantially zero back pressure as recorded by the gauge 30. This experiment was carried out at several air speeds for each of the whistles illustrated in figures 9a to 9j. The whistle of figure 9b was a commercially available Referee's whistle, that of figure 9c was a commercially available membrane pressure-release whistle, that that of figure 9g was a commercially available Scout's whistle. The other whistles are new per se. The table below shows the results. The dimensions shown in figures 9a to 9j are in mm. The design of figure 9j is preferred although those of figures 9a, 9e, 9h and 9i may also be suitable. The other whistles in general required air speeds that are too high for our present use. NR. DESCRIPTION OF WHISTLE AIR dB CHAMBER REMARKS SPEED PRESSURE IN M/S IN BAR A WHISTLE 2.03 98 0 TONE WHISTLE 2.50 102 0 TONE WHISTLE 3.00 1 12 0 TONE B REFEREE'S WHISTLE 6.50 108 0 TONE REFEREE'S WHISTLE 8.00 125 0 VIBRATING TONE C MEMBRANE WHISTLE 5.00 85 0 NO TONE MEMBRANE WHISTLE 20.00 1 15 1.5 NO TONE D SMALL ALUMINIUM WHISTLE 0.3 88 0 TONE SMALL ALUMINIUM WHISTLE 0.5 90 0 TONE SMALL ALUMINIUM WHISTLE 0.7 107 0 TONE SMALL ALUMINIUM WHISTLE 0.9 105 0 TONE SMALL ALUMINIUM WHISTLE 1.0 100 0 NO TONE SMALL ALUMINIUM WHISTLE 1.2 120 0 TONE E SMALL COPPER WHISTLE 3.0 128 0 TONE F LARGE COPPER WHISTLE 3.0 128 0 TONE G SCOUT'S WHISTLE 6.0 107 0 TONE SCOUTS WHISTLE 7.0 1 18 0 TONE SCOUT'S WHISTLE 10.0 129 0 TONE SCOUT'S WHISTLE 15.0 135 0 TONE H LARGE COPPER WHISTLE 0.5 102 0 TONE LARGE COPPER WHISTLE 0.7 1 10 0 TONE LARGE COPPER WHISTLE 1.0 1 10 0 TONE LARGE COPPER WHISTLE 1.2 105 0 TONE LARGE COPPER WHISTLE 1.3 97 0 NO TONE I ALTERNATIVE COPPER WHISTLE 0.5 90 0 TONE ALTERNATIVE COPPER WHISTLE 0.7 95 0 TONE ALTERNATIVE COPPER WHISTLE 1.25 97 0 TONE ALTERNATIVE COPPER WHISTLE 1.7 1 10 0 TONE ALTERNATIVE COPPER WHISTLE 2.5 105 0 NO TONE J PREFERRED WHISTLE 1.0 1 15 0 TONE PREFERRED WHISTLE 1.6 129 0 TONE PREFERRED WHISTLE 3.7 130 0.1 TONE

Claims: CLAIMS 1 . An instrument that produces an audible tone in response to passage of a gas at a flow rate below 600 ml per second. 2. An instrument according to claim 1 , that produces an audible tone in response to passage of a gas at a flow rate below 100 ml per second. 3. An instrument according to claim 2, that produces an audible tone in response to passage of a gas at flow rates throughout the range 40 - 100 ml per second. 4. An instrument according to any preceding claim, in which the tone is between 100 and 10000 Hz. 5. An instrument according to any preceding claim, in which the intensity of the tone is at least 60 dB. 6. An instrument according to any preceding claim, in which the sound generator comprises a fipple. 7. An instrument according to claim 6, in which the fipple has a cross-sec onal area of from 30 - 150 mm 2 . 8. An instrument according to any preceding claim which comprises a tube having a closed end. 9. An instrument according to any preceding claim, which acts as a Helmholtz resonator of resonating volume from 700 - 3000 mm 3 . 10. An instrument according to any preceding claim having an airway through which the gas must pass and which leads to a sound generator, the cross-sectional area of the airway being" from 2 - 10 mm 2 . 1 1 . A pressure relief valve incorporating an instrument according to any preceding claim. 12. A pressure relief valve according to claim 11 , in which all gas released through the valve passes through the instrument. 13. A pressure relief valve according to claim 11 or 12, which opens at a pressure between 2.5 and 5 bar. 14. An inflation tool comprising a pressure relief valve according to any of claims 11 - 13, means for connection to a source of pressurized gas, and an outlet pipe; the pressure relief valve being positioned between the means for connection and the outlet pipe. 15. An inflation tool according to claim 14, which additionally comprises a pressure indicator, the greatest restriction to gas flow through the tool being upstream of the pressure indicator. 16. An inflation tool according to claims 14 or 15, which additionally comprises means for controlling the flow of gas therethrough. 17. Use of an instrument according to any of claims 1-10 or a pressure relief valve according to any of claims 11-13 for inflation of a flexible hollow sealing member that can be inflated to seal a gap between first and second articles. 1 8. Use according to claim 17, in which the flexible hollow sealing member has a hole directly through a wall or between walls thereof through which hole a tube can be inserted to introduce pressurizing medium into the member, and means by which the hole is automatically sealed on withdrawal of the tube. 19. Use according to claim 17 or 18, in which the first article comprises a pipe or a cable. 20. Use according to claim 19, in which the second article comprises a duct or at least part of a splice case or pipe enclosure.

Inventors: KEUSTERMANS ERIK, ROOSEN DIRK, WAMBEKE ALAIN, KEUSTERMANS, ERIK, ROOSEN, DIRK, WAMBEKE, ALAIN
Applicants: KEUSTERMANS ERIK, RAYCHEM LTD, RAYCHEM SA NV, ROOSEN DIRK, WAMBEKE ALAIN, KEUSTERMANS, ERIK, N.V. RAYCHEM S.A., RAYCHEM LIMITED, ROOSEN, DIRK, WAMBEKE, ALAIN
Application year: 1994
Main classification: F16K37
IPC codes: F16K17, F16K37, H02G15